1. Field of the Invention
The invention relates to rapid curing, blemish-free epoxy coatings.
2. Description of Other Relevant Materials in the Field
Epoxy resins constitute a broad class of polymeric materials having a wide range of physical characteristics. The resins are characterized by epoxide groups which are cured by reaction with catalysts or curing agents to provide cured epoxy resin compositions with certain desirable properties.
U.S. Pat. No. 4,051,195 to W. F. McWhorter teaches curable epoxy resin compositions comprising (1) a blend of an epoxide resin and a polyacrylate or polymethacrylate ester of a polyol wherein the ester contains more than one terminal acrylate or methacrylate and (2) an aliphatic polyamine curing agent. The weight ratio of epoxide resin: ester is 100:5 to 100:100. The aliphatic polyamine is incorporated into the resin composition in a specified amount. The epoxy resin compositions are said to cure rapidly even at low temperature and are useful as coatings and adhesives.
U.S. Pat. No. 4,528,345 to H. G. Waddill teaches a method for making weather-resistant epoxy coatings. The method comprises prereacting a cycloaliphatic diepoxide resin with aminoethylpiperazine or a mixture of aminoethylpiperazine and polyoxyalkylenepolyamine in an amount which is balanced to give the maximum level of primary amine reaction without yielding an excessively viscous reaction product. The prereacted product is reacted with a curing amount of a polyoxyalkylene polyamine and an accelerator.
U.S. Pat. No. 3,875,072 to H. G. Waddill teaches an accelerator for curing epoxy resins. The accelerator comprises piperazine and an alkanolamine in a weight ratio of 1:8 to 1:1. A number of alkanolamines are taught. U.S. Pat. No. 4,195,153 to H. G. Waddill teaches an epoxy resin curing accelerator comprising a mixture of N-aminoethylpiperazine (AEP) and triethanolamine (TEA). U.S. Pat. No. 4,189,564 to H. G. Waddill teaches a non-crystallizing accelerator for curing epoxy resins. The accelerator comprises a mixture of 10 to 20% piperazine, 5 to 10% N-aminoethylpiperazine and 65 to 80% triethanolamine. The accelerator is sold commercially as Accelerator 399 by Texaco Chemical Co. The accelerator is said to be synergistic for accelerating the curing of a polyglycidyl ether of a polyhydric phenol cured with a polyoxyalkylene polyamine at ambient or elevated temperatures. Such amines include polyoxypropylene diamines of the formula: EQU NH.sub.2 CH(CH.sub.3)CH.sub.2 [OCH.sub.2 CH(CH.sub.3)].sub.x NH.sub.2
wherein x ranges from 2 to 40. Such amines also include polyoxypropylene triamines of the formula: ##STR2## wherein R is a lower alkyl and x+y+z ranges from 3 to 40.
These diamines and triamines may be synthesized according to U.S. Pat. No. 3,654,370 to E. L. Yeakey which teaches a method comprising a nickel, copper and chromium catalyst for aminating polyols.
U.S. Pat. No. 3,236,895 to J. M. Lee and J. C. Winfrey and U.S. Pat. No. 3,462,393 to Legler are pioneer patents. They describe a series of amine compounds which are solids or liquids and having utility particularly in curing epoxy resins. The amine compounds have the general formula: ##STR3## wherein R's ae selectively defined as hydrogen, alkyl radicals and alkylene oxide radicals and x and m are defined integers.